As a method of manufacturing the metal product of a given configuration, the method of casting, forging, rolling, and machining, etc are given as examples. However, a powder metallurgy process is frequently used, in which a metal powder (powder) is used as a metal material, and a powder compact is obtained by press-molding this metal powder and thereafter this powder compact is heated and sintered, for the metal product having a precise and complicated shape or the metal product requiring a particular material characteristic like a magnetic component.
In this powder metallurgy, the metal powder with a particle size of 1 μm to 100 μm manufactured by an atomizing method is mainly used (see patent document 1). The metal powder manufactured by the atomizing method has a powder particle with an approximately spherical particle shape. However, this spherical-shaped powder has a high flowability, with little friction between powder particles, and this is suitable for press-molding by charging into a metal mold. Therefore, in the powder metallurgy, the spherical-shaped powder is mainly used.
FIG. 5 schematically shows a manufacturing step of the metal product by a conventional powder metallurgy. As shown in this figure, a spherical-shaped metal powder 11 manufactured by an atomizing method is used in a sintering material. This metal powder 11 is molded/solidified into a given configuration by press-molding using the metal mold (compacting molding).
Usually a binder (bond) is used for molding. The binder is previously mixed in the metal powder. Alternately, a spherical-shaped granule (cluster sphere) of a prescribed size is granulated by the metal powder and the binder, and this granulated material is press-molded into a given configuration.
A molded powder compact (molded/solidified product) 31 is subjected to sintering processing at a high temperature after passing through a drying step, etc. By this sintering, the powder particles are partially fusion (diffusion)-bonded to be integrated, and a metal product 32, with the configuration solidified finally, is obtained.    Patent document 1: Japanese Patent Laid Open No. 2002-294308